This paper discusses the functional and technological opportunities associated with mobile recommendation systems. These are systems that help a mobile user or a group of mobile users with decisions that they encounter 'on the go.' Examples include consumers making purchasing decisions in retail stores, or students having ad hoc meetings to decide on assignment workload. We discuss key findings from behavioural decision theory to provide a set of functional requirements. This is followed by an exploration of technological options to implement mobile recommendation systems. The paper concludes with a discussion on how the user acceptance of these systems can be meaningfully measured and improved.